Precision longitudinal cutting of large, elongated, workpiece sheets or plates typically is accomplished by gripping the workpiece in a vise assembly and cutting the same with a cutting device, such as a band saw. Conventional plate band saw apparatus 10, as shown in FIGS. 1A and 1B, includes a base fixture or cutting table 11 having a generally planar support surface 12 upon which the elongated workpieces to be cut (not shown) are supported. Further, band saw apparatus 10 includes a saw carriage assembly 13 movable in a longitudinal direction along the base fixture. Saw carriage assembly 13 houses a flexible continuous loop saw blade 14 (shown in phantom in FIG. 1A) which is mounted around at least two wheels or pulleys 15, one of which is driven. Typically, two or more blade guide assemblies are mounted to saw carriage assembly 13 between the wheels and slidably engage the saw blade to orient it in a cutting orientation. The section of saw blade 14 intermediate the saw blade guide assemblies is called the "cutting stretch."
During motion or advancement of the blade, either the bandsaw blade and/or the workpiece is displaced relative to the other along a guided path known as the "cutting line" which is the center line of the desired line of cut. Typically, however, in bandsaw apparatus specifically suited for cutting elongated plate workpieces along the longitudinal direction thereof, saw carriage assembly 13 is arranged to be moved longitudinally along the cutting table in the direction of arrows 25 to engage the workpiece by suitable drive means (not shown). Thus, in these cutting operations, the saw carriage assembly is longitudinally displaced along the cutting table, which moves the cutting stretch and hence the saw blade along the cutting line.
To enable movement of the continuous loop blade longitudinally along the cutting table, an elongated blade receiving slot 16 is formed in support surface 12, coincident with the "cutting line", which receives the rotating blade therethrough. This permits the carriage assembly, and hence, blade 14, to freely reciprocate along slot 16 without any interference of the blade with the table.
Receiving slot 16 extends through support surface 12, and is formed between a substantially vertical wall of a longitudinal channel 17 in base cutting table 11 and an elongated central beam 18 received in channel 17. Further, a top surface of central beam 18 and a top surface of the base fixture collectively form support surface 12. Normally, one end 19 of central beam 18 is fixedly mounted to cutting table 11, while an opposite end 20 is movably supported atop a bottom wall 21 of channel 17 through two sets of jack screws 22 and 23, the distal ends thereof which contact the bottom wall to elevate or raise the top surface of central beam 18. This arrangement enables maintenance replacement of the loop blade, as well as leveling of the support surface.
In recent years, considerable effort has been directed toward enhancing the cutting efficiency and precision of band saws. While these goals have been accomplished for the most part, one reoccurring problem often encountered with these conventional band saw apparatus is that access to the continuous loop blade for maintenance and replacement purposes is extremely limited. Due to the nature and arrangement of the cutting table, and the elongated slot, the installation and removal of the blade is a time consuming and laborious practice.
Typically, as illustrated in FIG. 1A, the loop blade 14 is removed from the wheels so that an end of blade 14 can slide along the interspace between central beam 18 and base fixture channel 17. The first set of jack screws 22 is unscrewed or loosened to a raised position (FIG. 1A) which severs supportive contact between the distal ends thereof and the channel bottom wall 21. This causes all the suspension weight of the central beam to shift to the second set of jack screws 23. Band saw blade 14 is then allowed to pass into a "capture zone" 24 between the first set and the second set of jack screws.
Subsequently, the first set of jack screws 22 is reengaged with the central beam for supportive contact with bottom wall 21. The second set of jack screws 23, hence, can be removed or unscrewed to a raised position (FIG. 1B) which similarly causes all the suspension weight of the central beam to shift back to the first set of jack screws 22. This opens the other side of the "capture zone" so that bandsaw blade 14 can be retrieved therefrom. During installation of the loop bandsaw blade, the reverse procedure is applied.
This rather primitive sequence or series of steps is quite laborious and time consuming for technicians to exercise. Such practice causes production downtime to increase, which is especially critical in situations where the loop saw blades need to be replaced frequently.